Most vegetable crops are hybridized. Separate male and female inbred lines are developed that are substantially homozygous. Each inbred parent makes its own genetic contribution to the hybrid offspring and the resulting plants exhibit heterosis, or hybrid vigor. The hybrid plants are typically larger and more vigorous, and produce more and/or larger fruit. However, since most vegetables are dicotyledonous, they are typically insect pollinated. Squash are generally pollinated by bees. During periods of cool weather, bee activity is reduced. In addition, in some production systems, such as greenhouse and tunnel production systems, large insect populations are not available for pollination. As a result of each of these circumstances, pollination suffers, with a consequent reduction in production of fruit.
In the past, numerous chemicals have been developed which have the effect of inducing parthenocarpy Parthenocarpic plants will set fruit without having first been pollinated. However, many of these chemicals are auxins (plant hormones) and all of them have other, unwanted, effects upon plants or upon the production environment.
Spontaneous parthenocarpy has occasionally been observed in plants. However, in most species this phenomenon does not occur reliably and reproducibly. Accordingly, a continuing need exists for natural, genetic systems for causing parthenocarpy to occur in vegetable crop plants.